In Part 1 of the article series, we introduced an easy way to identify the soil type in your backyard, terrace garden or planting pots. In this Part 2, we will discuss the next step - how to determine soil health. There are 3 main determinants of soil health: 1) Stability of Soil Aggregates, 2) Microbial Activity and 3) pH Value. While there are comprehensive lab analyses that can be carried out, these may not be viable for home farmers or kitchen gardeners. Below are some recommendations for some simple tests that can carried out to test the health of your soil.
Soil aggregate stability offers a soil structure, which allows optimum movement and storage of gases, water, nutrients, and microbial activity. Good soil aggregate stability helps reduce erosion and compaction, holds a healthy amount of water and air, and enhances plants access to nutrients and minerals. Keeping soil healthy and stable is an important part of ensuring produce quantity and quality.
This simple test can be carried out by placing the soil samples in a handmade sieve (colander), with a very dense cloth (weave gaps should be around 0.05 mm). Dry soil is placed inside this sieve and then submerged in water for 10 minutes to test the stability of the aggregates. This is done to mimic what happens during rainy season.
If the aggregates are stable, most of them remain in the colander. Else, a significant amount of soil is moves through the cloth and indicates that the soil is prone to loss caused by erosion. In this case, you can improve the aggregate stability by increasing levels of organic matter such as manure and mulching.
While strong soil aggregates form naturally with plant roots and microbial activity, tillage can quickly break soil aggregates apart. Also, note that soil aggregates take time to form, so you should measure soil stability once every 3 to 5 years.
Why is Microbial Activity important?
Natural soils are habitats for tens of thousands of microbial species. They contain an incredible diversity of bacteria, fungi, viruses, and other organisms.
Soil microbes are important contributors to healthy soils and disease suppression. Presence of active soil microbes indicates:
Bury bags of green tea (easier to decompose) and red tea (take longer to decompose due to its higher content of lignin) 8 cm deep in your garden patch. If contents of both tea bags decomposed substantially within a given time, the soil is healthy (because of adequate microbial activity). If red tea has not decomposed as much as the green tea, then the microbial activity in the soil is less and needs to be improved.
To ensure adequate activity, you should create a moist soil habitat, with access to air spaces and sufficient organic plant material. It is also important to remember that there is a noticeable decline in microbial activity when there are more agrochemicals in the soil. So, yet another reason to skip the chemical fertilizers and pesticides. In addition to these efforts, there are studies suggesting that fish emulsions as well as bio-fertilizers accelerate microbial activity and, subsequently, improve the soil health.
Soils can be naturally acidic or alkaline, and this can be measured by testing their pH value. The pH scale is a numeric scale used to specify the acidity or basicity (alkalinity) of a substance (especially, liquids). Soil pH impacts the amount of nutrients and chemicals that are soluble in water, and thus the amount of nutrients available to plants for absorption. Having the correct pH (values between 6-7) is critical for healthy plant growth as well as quality of produce.
Soil pH Test
As a home gardener, it is important to test your Soil pH. You will need glassware, water, vinegar, and baking soda. Get a soil sample 4-6 inches below the surface. Remove the larger soil particles like leaves, stones, debris, etc. Mix soil and water in 1:1 ratio. Add ½ cup of vinegar. If the soil fizzes or bubbles, your soil is alkaline. Take a fresh soil sample and mix with water in 1:1 ratio. Add ½ cup of baking soda. If the soil foams or bubbles, your soil is acidic. If you test your soil using vinegar and baking soda and neither test produces much of an effect, your soil is probably in the neutral range and is pH balanced. Alternately, you can also dilute the soil in water and use a pH strip to get a more accurate reading of soil pH.
We are happy that you are on your way to becoming an urban farmer or kitchen gardener. Read Part 3 of this article series, where we will look at maintaining Soil Health in more detail. Also, do revisit Part 1 for a refresher on how to identify your soil.